Despite being a little awkward to handle as they include the running boards, the rear wings were quite straightforward to attach to the body and are a very good fit, although there were one or two minor difficulties.
The first job was to mark the reference points on the body sides (measurements given in the NG build manual). Then the inside flanges of the wings were marked and drilled to take the fixing bolts and screws (I replaced mine with stainless steel ones).
There are two Running Board brackets each side which bolt to the underside of the chassis (photo 2, see also Chassis Diagrams). With these brackets fitted, the running board and wing could be "rested" on them and positioned but a helper was needed to support the rear end while the position of the first hole was marked at the front.
Then, with the wing attached by this front bolt and supported by the brackets, it was possible to mark the positions of the holes up to the tops of the wings (supporting the wing slightly to line it up with the upper reference mark). Once these holes were drilled and the wing re-fitted, the remaining holes at the back were marked (measuring and adjusting each wing to make sure both sides matched). I discovered that only one fixing point goes into the valance instead of two (photo 3) so there are 10 bolts and 1 screw each side (not 9 bolts and 2 screws as in the manual).
Having fixed the wings to the body there were just two holes each side to be drilled up through the running boards so that they could be fixed to the brackets with countersunk bolts (photo 4). These holes should be equidistant from the side of the main body. With these final bolts fitted, the running boards feel very solid indeed!
Note that it is worth re-checking the position of the brackets (square to chassis and distance between them) and hold a block of wood on top of the running board to save splintering of the GRP when drilling through from underneath.
The running board part of each rear wing requires tread strips to be fitted. These are made from aluminium with rubber inserts (see Running Boards).
One option (which I prefer) for the rear lights is to use Light Pods fitted in the rear of the wings.